33. Nasir Al-Din Tussi
(597-672AH/1201-1274AD)

He was one of the few extraordinary scientists to have flourished in the 6th century H. and one of the distinguished Muslim scholars. He was as “Al-Allama” (The professor)(198).

Abu Jafar Muhammad Ibn Muhammad al-Hassan Nasir al-Din al-Tussi was born in Tus near Neyshabur(199) in Persia in 507 H (1201 AD), and died in Baghdad in 672 H (1274 AD). He studied under Kamal al-Din Ibn Yuness al-Musili and Abdelmun’im Salem Ibn Badran al- Mu’atazili(200).

He served as an astronomer to the governor Nacir al-Din Abderrahman Ibn Abu Mansur in Sartekht. He attained a privileged position in his time and was honored by the Caliphs and sat with Emirs and Viziers. He was as a result smitten by the jealousy of his fellow men and was defamed. As a consequence he was sentenced and imprisoned in the castle of “Alamut”, but allowed to continue his researches. It was in its reclusion that he compiled his most interesting books.

When Hulagu Khan, the Mongolian ruler, took hold of Baghdad, in 656 H (1258 AD), he wanted to benefit from his Abbassid enemy scientists. So, he freed Tusi, favored him and appointed him as administrator of waqf (religious bequests). Later, Tusi was appointed at the head of the observatory of Maragheh (Iran), build at Tusi's request. In this observatory, he supervised the work of many astronomers, brought by Hulagu from different regions of the world, including al-Muayed al-Urdi from Damascus, al-Fakhr al Maraghi from al-Musil, Najm al-Din al-Qazwini, and Mohi al-Din al-Maghribi. This observatory was famous for its sophisticated instruments and its higher observational capacity and for its splendid library that contained books pillaged from Baghdad, as-Sham and the Arabic Peninsula. Its books were estimated at 400,000 volumes(201).

Scientific Contributions

Tusi wrote on trigonometry, astronomy, algebra, and on the manufacturing and use of astrolabes. He was the first to separate trigonometry from astronomy, making it an independent science. He came up also with new evidences for various astronomical matters. He also presented new evidence for various astronomical issues. He was the first to use the six cases of the spherical right-angled triangle(202). Cara de Faw says that Tusi simplified and clarified trigonometry in his treatise “As-Shakl Ar-Rubai”. First, he used the methods of Manalaus and Ptolemy, then used his own methods, showing their results. The rule he called “the rule of complementary forms” differs from the Ptolemaic theory on the rectangles(203).

The genius of Tusi in geometry matched his genius in astronomy(204). He excelled in dealing with parallelograms, basing his demonstrations on hypotheses. Sarton says that Tusi demonstrated in his treatise “at-Tadkira” numerous geometric matters. He was characterized in his researches on geometry by his mastery of the basic principles related to geometry, especially concerning parallelograms(205).

He made important contributions and additions in astronomy. He clarified a number of astronomical theories, and criticized the "almajest" treatise and suggested an astronomical system simpler than the Ptolemaic one. Thus, he paved the way for the reforms brought up by Copernicus later. He also wrote treatises on the celestial sphere and the planets system.

Major Works

Nasr al-Din wrote on trigonometry, astronomy, algebra, geometry, mathematics, calendars, medicine, geography, logic, ethics, music and other subjects. He also translated some of the Greek books and made comments and critics on their topics.

Among his most famous books there are :

-“Kitab Shakl al-Kitaa” (The form). It was the first book to differentiate between trigonometry and astronomy. Cara de Faw says about it : “it was translated into Latin, French and English and constituted a reference for the Europeans for many centuries.”

-“At-Tadkira an-Naciria” It is a general reference book on astronomy in which the author explained a number of astronomical theories, and criticized Ptolemy's “almajest”. Sarton admits that this criticism was a proof of Tusi’s genius and deep knowledge of astronomy.

-“Zij-i Ilkhani” A table of planetary movements containing the calculations of the observations he made during 12 years.

- “Kittab Kawaid Al Handassa” (The rules of geometry)

- “Kitab fi Al Jibr wa al-mukabala”.

- “Kitab dahirat al-falak” (The astronomical phenomena).

- “Kitab tahrir al-manadir” in optics.

Tusi wrote his books in Arabic and Persian and were translated into Latin and other European languages in the Middle Ages. Most of them were printed.

Tusi was indeed one of the greatest Muslim scientists and one of their prominent mathematicians. He contributed a lot to the progress of sciences, especially astronomy and mathematics, His books constituted references for many centuries and gained a wide reputation for their author’s precious contributions.